1. Field of the Invention
The present invention relates to an air deflector. More particularly, the present invention relates to an air deflector having multiple airfoils disposed in tandem to the direction of travel and having increasing pitches.
2. Description of the Prior Art
Air deflectors came into general public acceptance during the seventies when the trucking industry was faced with escalating transportation costs due to rising fuel prices.
The recreational filed, also feeling this bite, wanted the same technology to benefit them, so a market was created by using scaled down foils and deflectors to fit automobiles and pick-up trucks which pulled travel trailers.
These RV market was able to find some savings in fuel expenses with these devices, but not much in the way of stability, traction, and reduced turbulence. Although, not nearly to the percentile extent as the trucking industry enjoyed, for two main reasons: height and width differential.
First height. Although, there is much variety in size, most tractors are only about three and one half feet lower than the trailers they pull, whereas, cars and trucks can be as much a seven feet lower than their trailers. To be effective, air has to be deflected up at a much more extreme angle than their tractor trailer counterparts due to the increased wind resistance caused by the increased frontal area of the trailer.
In attempting to divert air high in such a short span (tow vehicle's roof to trailer), as stated supra, a foil must be mounted with a high angle of attack.
Second width. Most tractors are just as wide as their trailers, while cars and trucks can be three or more feet narrower than the trailers they pull, thus exposing additional frontal area to air resistance.
This resistance can be formidable as it has been calculated that on a level road with no wind, a tow vehicle pulling a travel trailer at highway speeds uses 50% of it power expended just to overcome air resistance.
Most airfoil devices have been helpful in the RV market, but the current technology in the deflectors and scaled down airfoils available today do not offer the best efficiencies. This, mainly because they overlook width differentials, and disregard aerodynamic principles.
By their design, single foils, and especially deflectors, create a vacuum pocket to form behind them which causes much of the air they are intended to deflect, instead, to "pinch in"which partially defeats the purpose.
Air deflectors tend to help somewhat with width differential because they "splatter" the oncoming air away in all directions, but they create a high amount of drag in doing so.
Airfoils available today are somewhat more efficient, but one of their problems, since they were initially designed for trucking, is that they supply little, if any, assistance to the width/drag dilemma. The sides (or fences) of these airfoil products run parallel to the direction of travel, and serve only to support the single foil-shaped component between them.
Numerous innovations for air deflectors have been provided in the prior art that will be described. Even though these innovations may be suitable for the specific individual purposes to which they address, however, they differ from the present invention.
A FIRST EXAMPLE, U.S. Pat. No. 4,867,499 to Stephan et al. teaches a tailgate for a pickup truck that includes three elongate, rectangular panels or louvers having an airfoil-shaped cross section pivotally mounted in a U-shaped tailgate frame conformed to be mounted on a pickup truck in place of the conventional tailgate. The louvers are linked to each other for coordinated pivotal movement about respective horizontal axes extending along the leading edge of the airfoil section between a closed position and an open position wherein the louvers project rearwardly from the frame to accommodate a substantially unrestricted flow of air through the tailgate. A reversible electric motor controlled from the cab drives the louvers in pivotal movement through a worm gear drive which holds the louvers at any selected position. An airfoil section wing is mounted at the rearward end of the truck cab in spaced relationship to the cab roof and sidewalls to reduce turbulence in air flowing towards the tailgate.
Stephan et al. teaches multiple airfoils that are not disposed in tandem to the direction of travel, but rather spaced vertically apart from each other in the direction of travel so that airflow thereacross is not laminar which creates turbulence so as to maximize boundary layer separation and the resulting eddies and slip caused thereby.
Wake formation at the trailing edges of the multiple airfoils of Stephan et al. is not eliminated by virtue of the fact that the air flowing over the multiple airfoils is not prevented from separating at the trailing edges thereof.
A SECOND EXAMPLE, U.S. Pat. No. 4,904,015 to Haines teaches a tractor and trailer coupled together in tandem towing relationship that is provided with an air deflector system attached to the tractor for aerodynamically reducing the drag on such combination by enclosing the space between the cab of the tractor and the trailer. A support means is attached to the frame of the tractor. A top air fairing is movably attached to the support means for extending from the top of the cab to the top of the trailer. Two side fairings are movably attached to the support means for extending from the rear of the cab to the trailer, and wherein the side fairings mate with the top fairing. A means is provided for moving the fairings from one position to another based upon the alignment between the trailer and the tractor.
A THIRD EXAMPLE, U.S. Pat. No. 4,995,575 to Stephenson teaches actuation and support mechanisms for wing trailing edge flap systems wherein each flap system has a stream-wise or chord-wise pair of geometrically similar flap support assemblies. Each of the flap support assemblies has a chord-wise aligned cantilever support beam fixedly attached towing structure. The beam incorporates multiple cam tracks for providing guidance and support to a movable dual carriage assembly upon which a wing trailing edge flap assembly is mounted. The dual carriage assembly comprises a fore-carriage which is articulatably connected to an aft-carriage. The wing trailing edge flap assembly is mounted upon the aft-carriage. Both the fore-carriage and the aft-carriage are individually supported by rollers constantly engaging a separate cam track for each of said carriages. For actuation of the dual carriage assembly and the Owing trailing edge assembly mounted thereon, a ball screw drive mechanism is incorporated between the cantilever beam and the dual carriage assembly.
A FOURTH EXAMPLE, U.S. Pat. No. 5,092,648 to Spears teaches a plurality of spaced gates in the airflow control system on top of the tractor cab that opens up to permit a flow of air to impinge on the front face of the trailer to exert a braking force to augment the braking force exerted by the wheel brakes to slow down the tractor-trailer assembly.
A FIFTH EXAMPLE, U.S. Pat. No. 5,232,260 to Lippard teaches a pickup truck bed that has a split tailgate construction having a first gate member pivotally mounted in a parallel relationship relative to a second gate member positioned above the first gate member. The first gate member is arranged for pivotment to provide for airfoil orientation of the second gate member, with the first gate member arranged to permit pivotment of the first gate member against the floor of the pickup truck bed to permit airflow therethrough.
A SIXTH EXAMPLE, U.S. Pat. No. 5,688,020 to Burg teaches the pickup truck tailgate mounted drag reducing aerodynamic stabilizer or aero-stabilizer that acts as a turning vane(s) to direct air out over the tailgate thereby reducing drag, provides a stabilizing downward force on the aft end of the pickup truck during forward high speed operation of the pickup truck, and all of this is accomplished with an assembly that is out of the way when the tailgate is opened for carrying long boards or the like. The tailgate aero-stabilizer is a very simple, low cost, and easy to install device that can, in its preferred embodiment, be molded from one piece from weather resisting plastics or the like. An optional feature is a built in air braking device that can have as forces for actuation, in addition to aerodynamic forces, a torque spring, powered actuator, or other artificial force generator.
It is apparent that numerous innovations for air deflectors have been provided in the prior art that are adapted to be used. Furthermore, even though these innovations may be suitable for the specific individual purposes to which they address, however, they would not be suitable for the purposes of the present invention as heretofore described.